Manufacture of high antiknock hydrocarbons



Dec. 1, 1942. A. R. soLDsBY 2,303,735

MANUFACTURE 0F HIGH ANTIKNOCK HYDHOCARBONS Filed Feb. 10, 1940 21L2| 311 @Hugin I IFJ-1 f 1 N El D ARTHUR RoLossY INVENTOR HIS ATTORNE CONVERTER BY re. .Al/fm Patented Dec. l, 1942 MANUFACTUBE F HIGH HYDROCARBON Arum a. anlass'. amen, N. Y., minor, by

assignm ents, to The Texas Co New York, N. Y.. a corporation of Delaware Application February l0, 1940, Serial No. 318,219

(Cl. 19d-10) lilclaims.

This invention relates to a process of manufacturing high anti-knock hydrocarbons suitable for motor fuel.

'I'he invention contemplates the treatment of cracked or synthetic hydrocarbon mixtures containing mainly normal olefin and parafn hydrocarbons by alkylation and isomerization in a manner such as to obtain material improvement in the anti-knock characteristics of the hydrocarbon constituents.

'I'he invention also contemplates a process in which the hydrocarbon mixture to be treated is separated into individual fractions of comparatively narrow boiling range and each fraction separately subjected to alkylation.

In accordance with the invention a hydrocarbon mixture. containing a large proportion of straight chain hydrocarbons boiling over a subltantial range of temperature such as derived from the catalytic dehydrogenation of naphtha, or obtained by the catalytic conversion of carbon monoxide and hydrogen, or in some instances obtained from the thermal conversion of petroleum hydrocarbons, is fractionated into fractions of relatively narrow boiling range. Each fraction is subjected to alkylation with an lsoparailln hydrocarbon. preferably isobutane, and the alblated fractions are, in turn, subjected to some further treatment as may be desired.

According to one method of disposition these alkvlated fractions are fractionated to remove therefrom an intermediate fraction corresponding approximately in boiling range to the initial fraction from which it was derived. The resuit ing intermediate fractions, comprising mainly normal parailin hydrocarbons, are then subjected to isomerization to produce isoparailins. Isobutane formed in the isomerizationjs advantageously separated and recycled to the alkylation stage or stages, and the remaining isomerized hydrocarbons are blended with alkylated hydrocarbons to produce motor fuel of desired boiling range.

Instead of subjecting the intermediate fractions to isomerization they may be subjected to other forms of treatment, such as dehydrogenatlon. cyclization, etc.. to produce products of desired characteristics.

An important object of the invention, however, is to segregate hydrocarbon constituents of a feed mixture, such as described above, and to separately alkylate the segregated hydrocarbons rather than the composite mixture.

Y By separately alkylating narrow cuts of the results in the formation of a reaction mixture' containing alkylated hydrocarbons coextenslve in -boiling temperature range with normal paraiiin hydrocarbons ordinarily present in the feed. Due to this similarity in boiling temperature the normal parains and alkylated oleilns, therefore, cannot be completely separated from each other by fractional distillation. In other words, it is impossible by means of fractional distillation to segregate the alkylated hydrocarbons into fractions containing a relatively small proportion of normal parallns. the presence of which in large proportion may be undesired. due to their low anti-knock value.

'I'he present invention affords a means of segregating the alkylated hydrocarbons resulting from a charge mixture oi' the type in question so as to produce hydrocarbon fractions containing a high concentration of hydrocarbons having a high anti-knock value.

'I'he invention has particular application to the treatment of synthetic hydrocarbon mixtures such as mentioned above and which arecomposed largely of normal parafiins and normal oleiins ranging from normally gaseous hydrocarbons to liquid hydrocarbons boiling up to 1250-400 F. and even higher. It has been found that straightchain oleilns have more of a tendency than the branch-chain olens to build up into higher molecular weight compounds during the alkylation reaction. For example, a higher boiling range product is obtained from the alkylation of normal amylene than from the alkylation of isoamylene.

In other words, when alkylating a feed consisting essentially of branched chain liquid oleins. the resulting alkylate has a boiling range substantially coextensive with that of the feed. whereas when the feed consists largely of straight chain oleiins the resulting alkylate has a boiling range which is materially wider than that of the feed. In the latter case, the alkylate will include hydrocarbons boiling both below and above the boiling temperature range of the feed hydrocarbons, the higher boiling hydrocarbons usually feed mixture, rather than the entire mixture, it predominating.

Thus, where the feed mixture consists mainly of straight-chain hydrocarbons, alkylation of narrow cuts of the feed will produce products consisting essentially of compounds boiling above sentially free from aromatic and naphthenic constituents.

Moreover, alkylation prior to isomerization has the further advantage of removing substances, such as diolefins. hydrogen sulphide and amines, from the feed and which substances are injurious to the isomerisation catalyst. v

Reference will now be made to the accompanying drawing showing a flow diagram illustrating one method of practising the process of the invention.

Carbon monoxide and hydrogen, or a gaseous mixture thereof, in suitable proportions is passed to a catalytic converter I wherein the gaseous mixture is brought into contact with a conversion catalyst to effect conversion into hydrocarbons having a substantial olefin content.

The catalyst may -comprise metals such as cobalt,nicke1, iron, manganese or the oxides thereof, with or without a promoter such as thorium oxide. The catalyst is advantageously supported upon a material such as diatomaceous earth. Nickel, for example, is a preferred catalyst from the standpoint of increasing the olefin production relative to the production of saturated hydrocarbons. v

The carbon monoxide and hydrogen may be charged to the converter in the ratio of around one mol of carbon monoxide to about two mois of hydrogen. By decreasing somewhat the ratio of hydrogen to carbon monoxide it is Wssible to increase the yield of oledns produced.

The temperature maintained within the converter may range from around 330 to 400 F. and the reaction may be carried out under a pressure of about atmospheric, although somewhat higher pressures may be employed up to about ten atmospheres, for example.

Instead of a single converter the reaction may be carried outA in stages, using two or more converters in series. The products of conversion comprise normally gaseous and normally liquid hydrocarbons composed of around 60 to 70% by weight of hydrocarbons containing from one to about ten carbon atoms, with the remainder comprising higher boiling hydrocarbons.

The hydrocarbon products of reaction, including unreacted carbon monoxide and hydrogen. are passed to a stabiliser I wherein the unreacted materials, hydrogen and carbon monoxide, are removed in the form of a gas and which may be recycled ultimately to the converter I. Where there is an appreciable quantity of methane, ethane and ethylene present it may be desirable to remove these constituents from the conversion products.

The liquid stabiliser I accumulating in the bottom of the wherein the synthetic hydrocarbon mixture is separated into a plurality of fractions. The normally gaseous hydrocarbon fraction, mounting to about 8 or 10% of the mixture, is removed in vapor form from the top of the fractionator. This fraction will contain hydrocarbons, such as propane, butane, propylene and hutylene. and the olefin content may be around 50 to 55% by volume.

This gaseous fraction is conducted to an alkylation unit A1 wherein it is treated. in the presence of concentrated sulphuric acid, with isobutane from a pipe l. It is desirable to use an acid having a concentration of around 90 to 100% and, preferably, about 94 to 98% H2804. The temperature of alkylation may range from around to 90 F., but advantageously is about 80 F. Sumcient pressure is employed to maintain the reacting materials in the liquid phase.

is conducted to a fractionator I 76 Also, the ratio of isobutane to olens in the charge entering the aikylation reactor is at least about 1:1 and preferably about 3:1 to 5:1. The ratio of acid to total hydrocarbons in the reactor may be around 0.5 to 2.0 parts by volume of acid to one of hydrocarbon.

The alkylated hydrocarbons after neutralizing with an alkali solution are conducted to a fractionating unit F1 wherein they are stabilized to remove normally gaseous constituents.` A side stream comprising isobutane may be removed and recycled to the alkylation unit through pipe l previously referred to. The remaining alkylated material comprising high anti-knock hydrocarbons is drawn off and separately disposed of or blended with products subsequently produced in the process, as will be described later.

The remaining fractions removed from the fractionator I comprise normally liquid fractions removed as side stre'ams and which are drawn off to separate alkylation units As, Aa, As, and A, respectively.

The fraction passing to the alkylation unit A; advantageously comprises, hydrocarbons boiling within the range 80 to 150 F.; that passing to the unit A; will comprise hydrocarbons boiling within the'range 150 to 200 1".; that passing to the unit As will comprise hydrocarbons boiling within the range 200 to 250 F., while that passing to the unit As will comprise hydrocarbons boiling within the range 250 to 300 F. Additional higher boiling fractions may be produced, if desired, and likewise subjected to separate alkyiation.

It is also contemplated that .the boiling range of the fractions may vary somewhat from the foregoing, but usually each fraction will have an end boiling temperature not more than about 25 to 75 F. above its initial boiling temperature.

In each of the alkylation units the separate fractions are subjected to alkyiation with isobutane, as described above in connection with alkylation unit Ax.

The alkylated hydrocarbon mixtures after neutralization and upon issuing from the alkylation units are subjected to fractionation. For example, the reaction mixture from unit A: is passed to a fractionator F: wherein it may be separated into three fractions, namely, a low boiling fraction, an intermediate fraction boiling in the range to 200' F. and a higher boiling fraction boiling in the range 200 to 400 F. The intermediate fraction thus corresponds in boiling range to the fraction initially passing to the alwlation unit As. This intermediate fraction will be rich in normal paraffin hydrocarbons and s,sos,'rss

is passed to an isomerimtion unit I: wherein it is subjected to isomerisation in the presence of an isomerization catalyst such as aluminum chloride under conditions ofl temperature and pressure adapted to convert the normal parailln constituents to corresponding isoparamns. For example, this fraction may be subjected to contact with anhydrous aluminum chloride in the presence of a small amount of hydrogen halide in either the liquid or vapor phase at a temperature of about 200 F.

The higher boiling fraction as well as the lower boiling fraction produced in the fractionation unit F: will comprise alkylated hydrocarbons which may be separately disposed of or may be blended with the alkylated hydrocarbons produced in preceding or succeeding stages. In some instances it may be desirable to recycle the lower boiling fractions to the alkylation umts for retreatment with the alkylation catalyst in the presence of the isoparamn hydrocarbon.

Similarly the remaining feed fractions produced in the fractionator I and alkylated in the alkylation units Ax. As and As are passed to corresponding fractionating units Fn, Fe and Fs wherein they are subjected to fractionation to separate intermediate fractions corresponding in boiling range approximately to that of the initial feed fraction.

The resulting intermediate fractions are likewise passed to isomerization units Iz, I4 and Is wherein the paraffin fractions are subjected to isomerization.

The temperatures and other operating conditions are maintained in each isomerization unit suitable for the conversion of the parafllns undergoing treatment therein.

The products of isomerization from each fractionating unit In to Is, inclusive. are advantageously conducted to fractionating unit B. Substantial amounts of isobutane as well as hydrogen chloride may be present and these are separated in the fractionator B and may be recycled to the alkylation units and isomerization units respectively for reuse.

The remaining higher boiling isoparafiins produced in the fractionator 6 are drawn oil! and may be blended, all or in part, in a blending tank l. with the products of alkylation withdrawn from the fractionators Fi to Fs, inclusive.

It is, of course, contemplated that the products obtained at different stages in the process may be separately accumulated and disposed of for producing products having special characteristics such as safety fuel and aviation gasoline, for example.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims. y

I claim:

l. In the manufacture of motor fuel of relatively high anti-knock value from a broad boiling range gasoline fraction of comparatively low anti-knock value containing substantial proportions of normally liquid olefin and straight chain parafnn hydrocarbons, the method which comprises fra-ctionating the said broad boiling range gasoline fraction to separate the same into a plurality of normally liquid cuts, each having a relatively narrow boiling range and each containing a substantial proportion of normally liquid olen and straight chain paraflln hydrocarbons,

separately alkylating each of a plurality of said cuts with a low-boiling iacparamn boiling below the boiling range of the respective cut in the presence of an alkylation catalyst under alkylating conditions. whereby the isoparaln is alkylated by the oleiln of said cut to produce alkylated hydrocarbons of relatively high anti-knock value boiling larsely above the boiling range of said charge out, separately fractionating the hydrocarbon reaction products from each said alkylation reaction to separate the same into a higher boiling alkylate. lower boiling products, and a fraction of intermediate boiling range approximating the boiling range of the respective charge cut and containing mainly unreacted straight chain paraflin hydrocarbons and being essentially free from aromatic hydrocarbons, catalytically isomerising in the presence of an isomerization catalyst a plurality of said intermediate boiling range fractions obtained from the separate fractionation of the reaction products of said plurality of alkylation reactions to thereby convert straight chain parailins to branch chain parafllns of gasoline boiling range, and blending said plurality of alkylates and branch chain paraillns of gasoline boiling range from said isomerization to thereby produce motor fuel hydrocarbons of relatively high anti-knock value.

2. 'I'he method according to claim. 1, wherein the said low-boiling isoparatn employed for the said alkylation reactions is isobutane.

3. The method according to claim 1, wherein the isomerization of said intermediate ..oiling range fractions results in the production of isobutane in addition to branch chain parai'iins of gasoline boiling range. and at least a portion of said isobutane produced in the isomerization reaction is recycled to at least one of said alkylatlon reactions.

4. The method according to claim l, in which at least a portion of the said low-boiling products separated in the fractionation of the hydrocarbon reaction products of each alkylation reaction is recycled to the respective alkyiation reaction.

5. The method according to claim 1, wherein the said broad boiling range gasoline fraction is a synthetic hydrocarbon mixture obtained from the catalytic conversion of carbon monoxide and hydrogen, said mixture being composed largely 0L normal paramns and normal oleiins, and being essentially free from aromatic and naphthenic hydrocarbons.

6. The method of improving the anti-knock value of a narrow cut gasoline fraction of relatively low anti-knock value having an end boiling point not more than about 25 to '75 F. higher than its initial boiling point and containing substantial proportions of normally liquid oleiln and straight chain paraiiln hydrocarbons, which comprises reacting the said fraction with a lowboiling isoparailin boiling below the boiling range of said fraction in the presence of an alkylation catalyst under alkylating conditions, whereby the isoparailln is alkylated by the olen of said fraction to produce alkylated hydrocarbons of relatively high anti-knock value boiling largely above the boiling range of said charge fraction, iractionating the hydrocarbon reaction products of said alkylation reaction to separate the same into a higher boiling alkylate, lower boiling products, and a fraction of intermediate boiling range approximating the boiling range of the said charge fraction and containing mainly unreacted straight chain paramn hydrocarbons and being essentially free. from aromatic hydrocarbons, catalytically isomerlzing said fraction of intermediate boilins range in the presence oi' an isomerization catalyst to thereby convert straight chain paramna to branch chain paramns o! gasoline boiling range with the concomitant production oi isobutane, fractionating the products of isomerization to separate the isobutane and other normally gaseous products from a normally liquid isomerizatc boiling within the gasoline boiling range. and blending the said higher boiling alkylate with the said isomerizable to thereby produce a gasoline fraction oi substantially improved anti-knock value.

'1. The method according to claim 6, in which the said low-boiling isoparamn employed in the 15 alkylation reaction is isobutane. V

B. The method according to claim in which atleaataportionoftheiscbutaneproducedin the isomeriaation reaction is recycled to the alkylation reaction.

9. The method according to claim 8. in which atleastaportionoi'thelowerboilingproducta separated in the fractionation o! the alkylation reaction products is recycled to the alkylation reaction.

10. The method according to claim 8. wherein the said narrow cut gasoline fraction is a synthetic hydrocarbon mixture obtained from the catalytic conversion of carbon monoxide and hydrogen, said mixture being composed largely of normal paramns and normal olenns. and being essentially tree from aromatic and naphthenic hydrocarbons.

ARTHUR R. GOLDSBY. 

